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Thread: Occasional hum

  1. #141
    Join Date: Jan 2009

    Location: Essex

    Posts: 32,504
    I'm openingabottleofwine.

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    Quote Originally Posted by CageyH View Post
    This is very similar, if not the actual case - https://www.audiophonics.fr/en/diy-e...l-p-14211.html
    looking at the photos, all surfaces appear to be anodised. Thus you will need to re-tap the holes, and re-countersink the holes on the external surfaces. It is almost certain the fixings are metric (M3), so I would replace them with un-anodised steel screws. This should solve the problem

    Ideally I would remove the anodising from all mating surfaces, but the above should be sufficient.

    Good luck.
    Barry

  2. #142
    Join Date: May 2012

    Location: Toulouse, France

    Posts: 6,620
    I'm Kevin.

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    I have just disassembled the case, and removed all anodising from the mating surfaces, and rebuilt the case.
    Will it make any difference?

    I have my doubts, but it can’t hurt.
    Kevin

    Too busy enjoying the music....

    European loan coordinator for Graham Slee HiFi system components..

  3. #143
    Join Date: Jan 2009

    Location: Essex

    Posts: 32,504
    I'm openingabottleofwine.

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    Quote Originally Posted by CageyH View Post
    I have just disassembled the case, and removed all anodising from the mating surfaces, and rebuilt the case.
    Will it make any difference?

    I have my doubts, but it can’t hurt.
    Let us know the result Kevin.
    Barry

  4. #144
    Join Date: May 2012

    Location: Toulouse, France

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    I'm Kevin.

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    All I can tell you is that the resistance between the different parts of the case is now reading 0 ohms, where there was a very slight resistance before.
    I really doubt it will make a difference.
    Kevin

    Too busy enjoying the music....

    European loan coordinator for Graham Slee HiFi system components..

  5. #145
    Join Date: May 2012

    Location: Toulouse, France

    Posts: 6,620
    I'm Kevin.

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    As an update, I believe that the hum problem has been fixed.
    I replaced the 7805 voltage regulator with a Texas Instruments LM340T-5, as well as doing everything else listed here, and got quite a while I had had no issue.

    I am happy.
    Kevin

    Too busy enjoying the music....

    European loan coordinator for Graham Slee HiFi system components..

  6. #146
    Join Date: May 2012

    Location: Toulouse, France

    Posts: 6,620
    I'm Kevin.

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    But it came back…
    I removed all the internal ferrites. And it was no different.
    When doing this, I noticed a whiteish circle directly under one of the capacitors, so as a precautionary measure, I fitted some new Nichicon capacitors. At normal listening levels, I can not hear the hum. I really need to wind the wick up a bit.

    I am sure that I have not yet found the root cause, but as long as it does not affect the enjoyment of me listening to music, I can live with it.
    Kevin

    Too busy enjoying the music....

    European loan coordinator for Graham Slee HiFi system components..

  7. #147
    Join Date: May 2012

    Location: Toulouse, France

    Posts: 6,620
    I'm Kevin.

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    The hum is back.
    The AG1500 is back in the system. The hum has gone.

    So it is 100% mains based.
    I am thinking of building and fitting one of these - https://www.atlhifi.com/shop/assembl...nd-tested-pcb/

    Do you think it will work?
    Kevin

    Too busy enjoying the music....

    European loan coordinator for Graham Slee HiFi system components..

  8. #148
    Join Date: May 2012

    Location: Toulouse, France

    Posts: 6,620
    I'm Kevin.

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    This is the noise in question:
    Long version/real time (3 minutes - 33Mb) https://drive.google.com/file/d/14aw...ew?usp=sharing
    Condensed version (16 seconds - 3Mb) https://drive.google.com/file/d/11W0...ew?usp=sharing

    Any ideas on what this is, or more importantly, what is causing it?
    Kevin

    Too busy enjoying the music....

    European loan coordinator for Graham Slee HiFi system components..

  9. #149
    Join Date: Feb 2013

    Location: W Lothian

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    I'm Grant.

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    access blocked
    Regards,
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  10. #150
    Join Date: May 2012

    Location: Toulouse, France

    Posts: 6,620
    I'm Kevin.

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    Access updated

    And thanks.
    Kevin

    Too busy enjoying the music....

    European loan coordinator for Graham Slee HiFi system components..

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